Refrigeration compressor



Feb. 20, 1940.

\ F. K. SMITH El AL REFRIGERATION bOMPRESSOR Filed Feb. 5, 1957- s Sheets-Sheet 1 a F my BY a [SHE/0m ew- TTORNEY Feb; 20, 1940. F. K. SMITH Er AL REFRIGERATION COMPRESSOR Filed Feb. 3, 1937 3 Sheets-Sheet 2 Feb. 20, 1940. F. K. SMlTH :1 AL 2,191,326

REFRIGERATION COMPRESSOR- Filed Feb. '5, 1937 3 Sheets-Sheet 5 mvEN-roims ATTORNE Y Patented Feb. 20,

UNITED STATES" PATENT OFFICE 2,191,326 REFRIGERATION COMPRESSOR.

Frank E. Smith and Curtis M Brown, Tecumseh,

' Mich.

Application February'- 3, 1937, Serial No. 123,888

8 Claims. (Cl. 230-206) for compressing refrigerant vapors, a condenser connected to-the discharge side of the compressor to cool and liquify the compressed refrigerant, an evaporator or expansion coll in which the liquid refrigerant is vaporized with the absorption of heat, and a return or suction line leading from evaporator to compressor inlet to effect the recirculation of the refrigerant. Refrigerants now in common use, particularly in the so-called small units, have the property of mixing, either by process of suspension or solution, with the oil used to lubricate the compressor, with the result that oil tends to accumulate in the expansion coils, and interfere with satisfactory operation. :The commingling of refrigerant and oil, which cannot be .avoided altogether, since the compressor must be lubricated, has heretofore been par.-

tially offset -by providing the compressor with what may be termed an overhead inlet, as distinguished from a crankcase inlet, for the admission of refrigerant vapors which are. to be re-' compressed. The present invention, generally speaking, contemplates improvements in the overhead inlet type of compressor, to the end that its operation and functioning may be made 5 more eflicient, oil separation or limitation of commingling more positive, while insuring complete and adequate lubrication for all moving parts.

In achieving these general objects, the present invention proposes a number of novel features and improvements, which, for purposes of explanation, may be separately considered, although .it will be apparent, as this description proceeds,

that they are advantageously employed in conjunction with each other. It will also be understood that certain of these features may be independently employed, and may be applied to other types of compressors, without departing from the scope of the invention, as it is more fully set forth in the appended claims.

One feature of the'lnvention will be found to reside in a novel and improved means for effecting the separation of incidental quantities of oil which are returned to the compressor with refrigerant vapors. Other features of novelty reside in the provision of means for efl'ectively lu- ,si of Fig. 1;

bricating the various working parts of the compressor, su'ch as the main shaft seals, bearings, and piston and cylinder wall, without'excessive injections of oil into the compressed refrigerant. Still another feature of the invention is the pro- 5 vision of improved means for imparting to the piston and connecting rod assembly a high degree of dynamic balance and ease of manufacture. Other and further features of the invention will be pointed out as this specification pro- 10 oeeds with a discussion of a typical embodiment, illustrated in the accompanying drawings, wherein:

Fig. 1 is a front elevation of the compressor,

with a portion of the crankcase and associated 15 structure shown in section;

Fig. 2 is an enlarged section on the line 2-2 of Fig. 1, showing the sealing ring formation;

Fig. 3 is a slightly enlarged section on the line Fig. 4 is a fragmentary section on the line 44 I of F18. 3;

-Fig. 5 is a fragmentary section on the line 5-5 of Fig. 3, showing the oil pump impeller arm;

Fig. 6 is an enlarged fragmentary sectional 25 view showing the positioning of the oil grooves in the piston, and the piston disposed at the top of its stroke in the cylinder;

Fig. 7 is a section on the line 1-1 of Fig. 1,

with the upper portions of the compressor shown 30 in elevation; and

Fig. 8 is a section on the line 8-8 of Fig. 3, showing more fully the. disposition of the reservoir groove formed in the cylinder The compressor of the present. invention is ilg5 lustrated in the drawings as being of a single cylinder type having a cylinder block is integrally connected to a crankcase ll, although it will be understood that the novel features hereof may also be applied to multiple cylinder com- M pressors. The crank ,case M is formed with aligned bearings i2 and 63, receiving a drive shaft id, to which is keyed'or otherwise secured an eccentric it. A connecting rod it is formed at its lower end with 'a strap i-l disposed about $5 the eccentric l5, and with a small end bearing 88 at its opposite end which receives a wrist pin l9, projecting into suitable bearings formed in a piston 21. Rotation of the shaft It therefore serves to reciprocate the piston ii in the cylinder 50 bore 22.

A cylinder head 23' is disposed on the upper end of the block it and it here comprises a two. part structure including a head casting 24 and an interposed valve plate 25, both secured to respectively disposed to cover inlet and outlet ports 29- and 3|, which in turn are in fluid communication with inlet and outlet chambers 32 and 33 formed in the head casting 24 by a diametrically disposed partition wall 34.

The inlet and outlet chambers 32 and 33 are in turn connected, by registering orifices 31 and 38 formed in the valve plate 25, to inlet and outlet passages 35 and 36 formed vertically in the block l0. Laterally disposed holes 39 and 4i are formed in the wall of the block ill to intercept the passages 35 and 36 respectively, and thus provide means for connecting the compressor to the evaporator suctionline and condenser of the refrigeration system (not illustrated), to which it is assumed that the invention is applied.

It will be observed that the inlet passage 35' is in fluid communication with the crankcase ll through a drilled oil escape opening 42 of relatively small diameter; it being intended that refrigerant and oil, entering the compressor through the opening 39, will be appreciably separated in the passage 35. The refrigerant may flow through the described passages into the cylinder bore 22 during the downward movement of the piston 2|, while compressed refrigerantmay be discharged through the opening 4| durin :movement in the opposite direction.

Disposed in the lower portion of the inlet passage 35, and above the opening 42, is a baiile member 45. The member 45.is in the form of an inverted cup having an external annular flange 46 adapted to fit snugly in the bore 35, with the cylindrical wall of the 'cup having a clearance from thebore to, provide an annular well 41. It will be observed that the wall and-upper end of the cup are imperforate, except for the provision of two holes, one of which, designated by the reference numeral 48, is disposed at the bottom of the well and is of relatively small diameter. The other hole 49 is disposed adjacent the top of the well, and is of relatively large diameter, for a purpose which will presently be explained.

A wire screen or cup 5| is disposed at the upper end of the passage 35, and it protects the compressor from dirt ingress and also serves to provide a means for efiecting additional separation of oil from the incoming refrigerant. The head casting 2 3 is further formed with 2. depending bafl'le wall 52 located in the refrigerant vapor path, and the inlet opening 29 receives a pipe '53 also serving to eliminate oil globules from the refrigerant. All of these elements cooperate to reduce the quantity of oil which may enter the cylinder '22, and it will be'apparent that, as the oil is separated, it flows down the passage 35:3, collects in the well l'i, and may flow through the holes it and dd into the crankcase ii, through the opening 432.

The reason for mag the holes it and as of difierent size will now be explained in accordance with our understanding of the principle involved. When the machine is operating, a condition of pressure pulsation and liquid surge is set up in the crankcase i l, due to the movement of the parts and the changes in volume. This action tends to eject oil through the opening it, in a direction just reverse to that above described, and such reverse flow obviously is not wanted. The cup at, together with the limited size of the hole 42, minimizes ejection of oil into the passage 35, but mlghtnot, in the absence of additional improvements, serve to prevent some reverse flow under all operating conditions.

The size of the parts is, intended to be such that the amount of oil collecting in the well 41, for sa'y each cycle of operation, is not enough to fill the well to a point above the opening 49. This opening may therefore be regarded as a breather hole, and to the extent that gas compression occurs in the crankcase, the breather hole provides for reduction of such pressures as are developed, thereby making for smooth operation. The hole 49 is also sufficiently large that, even if it should be submerged below the level of the oil in the well 41, gravity flow of the oil in one direction, and gas in the other, may take place. A suitable size for such opening, in machines of the type herein illustrated, has been found to be about one-eighth of an inch diameter. 4

The hole 48, however, is. made of such size that, having in mind the operating conditions, it functions in accordance with the laws of fluid flow through a small orifice of negligible length; That is to say, when there is a surge from the crankcase toward the passage 35, the pressures on opposite sides of the orifice 48 are, or may be, substantially equalized, and hence no appreciable fiow of oil will take place, because the orifice is too small to admit of free flow under the force of gravity alone. When there is a pressure difierential across the orifice 48, caused by a reduction in pressure in the crankcase, oil in the well 41 may drain through the opening 48, under the influence of such pressure. A suitable diameter for this orifice has been found to be one-sixteenth of an inch.

It will be seen that the orifice 48 thus serves as a drain and a check valve requiring no moving parts, while the opening 49 serves as a drain when required, and a breather hole under all operating conditions. Conjointly, and in cooperation with the other elements of the machine, these apertures therefore serve to remove oil from the incoming vapors, and prevent the discharge of crankcase oil into the. refrigerant which is to bejcompressed.

The lubrication of the compressor is accomplished by means associated with the drive shaft assembly acting on the oil contained in the crankcase H. The bearing I2 is provided with oil inlet holes 55 which are supplied with lubricant splashed thereinto during operation. It will be noted that the bearing 12 is both a radial and thrust bearing, and the shaft M terminates therein, abutting the end thrust member 58. The bearing i3 is also provided with an oil hole 5? which communicates with a longitudinal slot 58 formed in the shaft M, and also a seal chamber 59.

' The seal chamber 59, through which extends the projecting end of the shaft M, is closed on the outer end by a cap plate 6!, held in place by bolts 62. The chamber 59 receives a seal unit comprising an end plate 63 clamped between the cap '38 and the end of the crankcase II, and a sealing ring 63 connected to the plate 63 by an expansible bellows 55. The sealing ring 64 is urged toward a shoulder 66 formed on the shaft Ml by a spring 67.

The ring ti is formed with an annular projecting portion 63 abutting the shoulder 66 to provide a gas tight lapped joint, thereby preventing leakage of oil and refrigerant from the crankcase ll It will, of course, be understood that the cavity formed between the inner face of the ring 65, the shoulder as, and theperipheral surface of the projecting portion 88 receives oil from the bearing hole 81. Heretofore, it has been en- :deavored to make a very tight Joint in packless compressor seals, but when a sumciently tight joint was obtained, as by lapping the contacting and relatively movable parts, no oil film could be developed therebetween. with the result that the carefully made joint would. beburned out, thus leading to the destruction of the seal.

Accordingly, the present invention provides the projecting annular portion 88 with a plane shoulder-contacting face, and non-concentric portions on the outer peripheral surface; so that,

as the shaft rotates, portions of the contactedshoulder are exposed to admit a fllm of oil. As

best shown in Fig. 2, this effect is herein obtained by providing the annular peripheral surface 88 with flattened portions II whichexpose segments of the shoulder during-operation. The 28 efficacy of the seal is thereby maintained, and the cause of burning out is eliminated.

As hereinabove noted, the portion of the shaft I4 disposed between thebearings' I2 and I8 receives an eccentric I5. One face of the eccentric is formed with an integral counterweight I8, while the other face is formed with a projecting hub 1-6. It will be noted that the hub is both radially and axially slotted, as indicated by the reference numerals I1 and I8, to form a resilient 80 sector I8. The lower surface M of the hub 18 is cylindrical, and is adapted to receive a removable-counterweight 82, which is secured thereto by bolts 83 extending vertically through the partially weakened'sector 18. The bolts also secure 5 a sheet metal oil slinger 84 to the. upper portion of the hub I6. 3 4

' The removable counterweight is provided so that-the strap I1 of the connecting rod I8 may be readily applied to the eccentric I5, by move- 40 ment over the hub I8. After such assembly is effected, the counterweight 82 is brought into contact with the surface 8i, and is loosely secured by insertion of the bolts 83. The entire eccentric, counterweight, and piston assembly is then inserted through the bottom of the crankcase II, and the shaft I4 is pushed through the eccentric and hub into the bearing I2. The bolts 83 are thereupon tightened to clamp the eccentric to the shaft, and, by virtue of the structure pro- 54) vided, the resilient portion I8 may yield to such strains as are imposed, thereby taking up the stresses without distortion of the eccentric I8 it= self. 'Upon operation of the compressor, the

counterweights and oil splasher 84 serve to de- 55 liver adequate quantities of lubricant to the bearings I2 and I3 andthe sealing ring 84, thereby preventing excessive wear on these parts.

The lubrication of the wrist pin bearing I8,

and also the lubrication of the strap bearing I1,

50 is accomplished by means of an oil pump formed on the eccentric I5. As best shown in Figs. 3, 4,

and 5, the eccentric is formed with a laterally projecting lug 8| provided with an angularly drilled hole 82 communicating with a smaller hole 5 83 which extends through the rim of the eccentric I5 at the mid part thereof. The connecting rod I8 is formed with an axially drilled. hole 84 leading from the strap I! to the wrist pin hearing I8. The strap bearing is formed with grooves or oil pockets 88 located on opposite sides of the lower end of the hole 84. Oil delivered through the hole 82 will, therefore, as the connecting rod reciprocates, find its way into the pockets 88,v and Y in place as the piston move will thus be delivered to the bearing I8. Since the b 81 is m r di p d w th respect to the radius and tangent taken through the end of the hole 88, oil entering the bore '82 during periods of immersion in the crankcase will be forced, by centrifugal action, toward the hole 88 as the eccentric rotates about the center 5 of the shaft I4. The force'resulting from the rotation of the oil in the bore 82 therefore drives such oil, when registry is obtained between the hole 88 and the pocket 88, into the pocket and thence up the hole 84 into the wrist pin bearing. 10 While the hole 88 is out-of registry with the pocket 88, centrifugal force acting on the oil tends to force the oil out against the surface of the strap I'I, thereby providing continuous lubrica- 1 tion for the lower hearing as well. 5

Another portion of the compressor requiring adequate lubrication is the surface of the cylin- .-der 22, which is contacted by the piston 2I. From what has been heretofore set forth, it will be apparent that negligible quantities of oil are 88 present in the gas undergoing compression, and

accordingly the lubrication of these surfaces is effected from the lower,on crankcase end, of the machine. Briefly stated, the lower end of the piston is made to convey oil up to the cylinder 28 wall, from whence the oil is disseminated in such manner as to lubricate the entire surface.

Referring to Figs. 3, 6, and 8, it will be observed that the piston 2| is formed adjacent its lower extremity with a groove I8I of angular 30 formation, a second similar groove I82 disposed thereabove, and a pair of semi-cylindrical grooves/ I88 and I84 disposed at still higher points. In Fig. 3, the piston 2I isishown at the lower end of its stroke, while in Fig. 6, the piston is shown, 35 on a larger scale, as disposed at the upper extremity of its stroke.

- Whileca very slight clearance, of say two to four ten-thousandths of an inch, is provided between the main body of the piston andcylinder 40 wall, the lower portion of the piston, particularly below the-groove I82, is provided with a greater and progressively increasing clearance, thereby forming, in section, a tapered clearance notch I85 wh0se maximum width may be of the order 45 of say three thousandths of an inch, or appreciably more than the normal running clearance.

The upp r end of the piston 2|,is also formed with a has. band I88 of reduced diameter which terminates in a groove I81, otherwise similar to I58 the grooves I88 and I84, thereby providing a second pocket I88 between the upper end of the piston and the cylinder wall 22. A pair of circumferential grooves I88-are formed inthe cylinder wall 22, being interrupted to provide'a con- 85 I tinuous bearing surface in the cylinder bore for the positioning buttons III of the wrist pin I8,

as shown in Fig. 8. The "relation of the grooves formed in the piston 2I to the location of the grooves I88 is such that the groove I82 is aligned with the grooves. I 88 when the piston is at the upper end of the stroke (Fig. 6), and the upper groove I 81 is just barely aligned with the grooves I88 when the piston is at the lower end of the stroke (Fig. 8).

"The mode of lubrication through the action of these various grooves may be understood'by as-' suming that the piston 2I is at the lower end of the stroke, as shown in Fig. 3. The/splashing action caused by the counterweights and associ- 7i ated movingparts throws oilinto the groove Ni, and, due to the viscosity of the oil and the angular formation of the gr vs, the oil will remain upward. When the piston is in the position shown 6, the oil in f;

the groove IOI, in endeavoring to run out, contacts the lower portion of the cylinder wall 22, and spreads thereover due to natural surface tensionaction. By this time, the piston is again moving down, and, due to the wedge-like formation of the clearance opening I05, excess quantities of oil on the cylinder wall are squeezed through the normal clearance opening, and

thence into the groove I02, which during such period is spaced from. the grooves I09. On the next upward stroke, the oil so conveyed to the piston groove I02 is elevated to lubricate a new portion of the cylinder wall, and the excess is, at the top of the stroke, deposited in the grooves I09, which thereupon become reservoirsfor oil. These reservoirs are replenished as required, as operation continues, by a repetition of the foregoing steps.

Assuming the grooves I09 to be filled, it will be observed that-when the piston is at the lower end of the stroke, the upper groove I01 is in registry therewith, toreceive a'charge of oil, and, as the piston moves upward, the grooves I04 and I03 also receive oil for lubrication of the cylinder wall. Each upper piston groove thereupon serves to convey oil from the reservoirs I09.to the cylinder wall, thus maintaining adequate lubrication at all times.

As the piston 2| moves upward, some scraping action will occur, causing some of the deposited oil to flow into the pocket I08. If this pocket were not provided, there would be a possibility of excessive expansion of the piston over the head portion, with its attendant disadvantages. Additionally, the pocket catches and retains those quantities of oil which otherwise would be scraped off into the cylinder for commingling with the refrigerant undergoing compression.

In practical use of the invention, it has been found that compressors made in accordance herewith have been highly efficient, smooth in opera: tion, practically noiseless or free from knock", and so adequately lubricated at all running parts as to eliminate many of the dimculties hereto-' fore encountered in this type of service. While it.

has been found that the compressor is fully lubricated at all times, it has also been observed that very little oil is carried over into the condenser and expansion coils, thereby permitting such parts of the system to operate at a higher efficiency. It will, of course, be understood that some minute quantities of oil will remain entrapped or dissolved in-the refrigerant, but such amounts are readily returned, and are separated as they enter the compressor to prevent accumulation of oil in the refrigerant.

It will be understood that while, for the purpose of presenting to those skilled in the art the best mode now known to us to apply the principles of the invention to practical use, references have been made to the specific formation, relative locations, and dimensions of parts, it is not intended to restrict the invention to such details as stated, but to encompass within the scope hereof all such modifications, variations, and adaptations as are within the context of the following claims.

We claim:

1. The combination with a compressor having a crankcase, a cylinder block, and a head for the cylinder block, an inlet chamber formed in the head, a passage formed in the block and communicating with the chamber, of an oil drain extending between the passageand the crankcase, and an inverted cup disposed in the passage and posi- 2. The combinationwith a compressor having a crankcase, a cylinder block, a head for the cylinder block, an inlet chamber formed in the head,

and a passage communicating with said chamber formed in the block, of a drain hole formed at one end of said passage and connecting the pas- 1 sage with the crankcase, an inverted cup disposed over said drain and spaced from the wall of said passage to provide a well, and a plurality of apertures formed in the cup and positioned at different elevations with respect to said well.

3. The combination with a compressor having a crankcase, a cylinder block, and a head for the block formed with an inlet chamber, an inlet passage formed in the block and communicating at one end with the inlet chamber, of a drain hole formed in the opposite end of said passage and connecting said end with the crankcase, an inverted cup disposed over said drain and spaced from the wall of said passage to form a well, and apertures formed in the cup at progressively higher points with respect to said well,-the lowermost of said apertures being of the smallest diameter for the purpose described.

4. That improvement in refrigeration compressors of the type having a crankcase, a cylinder block formed with a passage in thereof, and a cylinder head having an input chamber in communication with the passage and the cylinder, comprising a drain hole of less diameter than the passage formed at one end of the wall said passage and communicating with the crankcase, a cup member positioned over said drain and in and spaced from the wall of said passage to provide a well for the accumulation of oil,

an orifice of small diameter formed in the wall of the cup adjacent the bottom of the well, said orifice being of such diameter as to resist the flow of oil therethrough in either direction during periods of surge from the crankcase toward said passage, and a breather opening formed in the cup adjacent the top of said well.

5. The combination with a compressor having a crankcase, a shaft in the crankcase, a cylinder block, and a piston reciprocably mounted in the cylinder block, an eccentric mounted on the shaft, a connecting rod formed with bearings at each end thereof respectively encircling the eccentric and a wrist pin forming a connection with the piston, said connecting rod being further formed with an axial hole extending between said bearing'., of a laterally projecting boss formed on one face of the eccentric and extending from the periphery thereof and at an angle to a radius or tangent drawn through said portion of the periphery, said boss being formed with a bore extending from the outer end thereof through said periphery, whereby, upon revolution of said shaft and eccentric, oil entering the outer end of said bore will be centrifugally forced between said eccentric and bearing and through said axial hole to lubricate said wrist p n.

6. The combination with a compressor having a crankcase adapted to contain lubricant, a shaft 'mounted in the crankcase, a cylinder block, a piston formed with a wrist pin mounted in the cylinder block head, an eccentric secured to the shaft, a connecting rod formed with bearings at each end thereof respectively encircling the cocentric and wrist pin, of means for lubricating said bearings with lubricant,contained in said crankcase, said means comprising a boss laterally extending from one face of the eccentric at a portion thereof remote from the center of the shaft, said boss extending from the-periphery of said eccentric in an angular direction with-respect to a radius and tangent drawn through the 1 the cylinder block, an inlet chamber formed in the head, a cylindrical passage formed in the block and communicating with the chamber, of an oil drain extending coaxially between one end of the passage and the crankcase, and an inso verted cylindrical cup disposed in concentric spaced relation to the wall or the cylindrical passage to form a well, said cup being secured in said pwsage over said drain, said cup being formed a with a drain aperture in the side wall thereof.

: mediate positions of the piston.

FRANK 8; In a compressorv having a cylinder wall, a crankcase adapted to contain lubricant, and a piston disposed in said wall for reciprocatory movement toward and away from the crankcase, means for lubricating the cylinder wall and pis- 5 ton comprising the formation of a tapered portion on'the crankcase end of the piston, oil receiving and transmitting grooves formed respectively at the lower and upper end of said tapered portion, the upper end of said piston being of w reduced diameter to provide a clearance and on retaining pocket, a circumferential groove in the piston at the lower end of said pocket, other oil grooves formed in the piston between said pocket and transmitting groove, and an oil reservoir 15 groove formed-in the cylinder wall and so positioned with respect to the length and the stroke of the piston as to be in registry with the lower end of said pocket at one extremity of piston movement, and in registry with the transmitting 2o groove at the opposite extremity of piston movement and with said other oil grooves at inter- 

